This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A242741 #17 May 17 2019 14:43:07 %S A242741 29131,119327070011 %N A242741 Primes p such that p^2 divides 15^(p-1) - 1. %C A242741 Base 15 Wieferich primes. According to Richard Fischer there is no other term up to approximately 5*10^13. %H A242741 Amir Akbary and Sahar Siavashi, <a href="http://math.colgate.edu/~integers/s3/s3.Abstract.html">The Largest Known Wieferich Numbers</a>, INTEGERS, 18(2018), A3. See Table 1 p. 5. %H A242741 R. Fischer, <a href="http://www.fermatquotient.com/FermatQuotienten/FermQ_Sort">Thema: Fermatquotient B^(P-1) == 1 (mod P^2)</a> %t A242741 Select[Prime[Range[1000000]], PowerMod[15, # - 1, #^2] == 1 &] (* _Robert Price_, May 17 2019 *) %o A242741 (PARI) %o A242741 forprime(n=2, 10^9, if(Mod(15, n^2)^(n-1)==1, print1(n, ", "))); %Y A242741 Cf. A001220, A014127, A123692, A212583, A123693, A045616, A111027, A128667, A234810 %K A242741 nonn,hard,bref,more %O A242741 1,1 %A A242741 _Felix Fröhlich_, May 21 2014